What are some issues I need to be aware of for using the Web Start Observing Tool on my Mac?

Posted by Andy Biggs, Last modified by Andy Biggs on 19 March 2015 01:33 PM

If the Observing Tool is started from a Mac, many users who are running OS X Lion (10.7) or later may find that clicking on the Web Start icon in a browser does not, as used to be the case, start the OT automatically. This turns out to be due to a feature of OS X named "Gatekeeper". Since Mountain Lion, this defaults to only allowing applications to run that have either been downloaded from the App Store or have an Apple Developer ID. As the OT does not have one of the latter, a Mac will force the user to manually open the application. The following is required to get the OT to run:

* Click on the Web Start icon in a browser. Both Safari and Firefox will download the .jnlp file (this happens very quickly and is therefore easy to miss) and Firefox will report that it could not be opened "because it is from an unidentified developer". Safari will do nothing.

* Open the Download dialogue of your browser. For both Firefox and Safari this is a square icon with a downward-pointing arrow that is located at the top right of the browser window. This will reveal the downloaded .jnlp file, but double-clicking it will fail to start the OT.

* Open the .jnlp file in a Finder window by clicking the magnifying glass symbol. Again, double clicking this will not work!

* Right-click on the .jnlp file and choose "Open With". It is likely that Web Start is set as the default and this should be chosen. You should now (finally!) be given the opportunity to open it and the OT should start.

At this point, your Mac should automatically create a shortcut icon on your Desktop. This should be used from now on to start the OT! Starting the OT from the Web Start icon on the download page will cause another .jnlp file to be downloaded and the above steps will need to be repeated.

One way to avoid all of the above problems is to simply switch Gatekeeper off using the "Security & Privacy" system preferences menu item. At the bottom of the General tab are three choices - selecting the third of these ("Anywhere") will cause Firefox and/or Safari to start the OT just by clicking the Web Start icon in a browser. This though is not recommended given the security implications.